Low-temperature Raman spectroscopy of sodium-pump rhodopsin from Indibacter alkaliphilus: insight of Na+ binding for active Na+ transport
| Autor: | Akiko Okamura, Takashi Kikukawa, Yushi Nakamizo, Hiroaki Baba, Masashi Unno, Tomotsumi Fujisawa |
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| Rok vydání: | 2021 |
| Předmět: |
0303 health sciences
biology Chemistry General Physics and Astronomy Active site Chromophore 010402 general chemistry 01 natural sciences 0104 chemical sciences Photoexcitation 03 medical and health sciences symbols.namesake Crystallography Ion binding Rhodopsin symbols biology.protein Salt bridge Physical and Theoretical Chemistry Binding site Raman spectroscopy 030304 developmental biology |
| Zdroj: | Physical Chemistry Chemical Physics. 23:2072-2079 |
| ISSN: | 1463-9084 1463-9076 |
| DOI: | 10.1039/d0cp05652a |
| Popis: | We carried out the low-temperature Raman measurement of a sodium pump rhodopsin from Indibacter alkaliphilus (IaNaR) and examined the primary structural change for the light-driven Na+ pump. We observed that photoexcitation of IaNaR produced the distorted 13-cis retinal chromophore in the presence of Na+, while the structural distortion was significantly relaxed in the absence of Na+. This structural difference of the chromophore with/without Na+ was attributed to the Na+ binding to the protein, which alters the active site. Using the spectral sensitivity to the ion binding, we found that IaNaR had a second Na+ binding site in addition to the one already specified on the extracellular surface. To date, the Na+ binding has not been considered as a prerequisite for Na+ transport. However, this study provides insight that the protein structural change induced by the ion binding involved the formation of an R108-D250 salt bridge, which has critical importance in the active transport of Na+. |
| Databáze: | OpenAIRE |
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